We propose to study the interaction of melittin and phospholipase A2 with model phospholipid membranes by using fluorometric, laser Raman, turbidimetric, and microcalorimetric techniques. We aim at establishing: 1. Whether these proteins express their action through modulation of the structural organization of the hydrocarbon chains of phospholipid bilayers, through modulation of their mobility, or through both mechanisms. 2. The state of aggregation and the conformation of the active form of the proteins. 3. The phospholipid parameters that control the rate of incorporation of the proteins. 4. The relative contribution of the electrostatic and hydrophobic forces to the protein-phospholipid interaction. 5. The occurrence of exchange of proteins between lipids. Our ultimate goal is to develop a framework in which the physiological effects of the proteins will be understood in molecular terms.